<section class="pf-c-nav__subnav{{#if nav-subnav--modifier}} {{nav-subnav--modifier}}{{/if}}"
  {{#if nav-subnav--attribute}}
    {{{nav-subnav--attribute}}}
  {{/if}}
  {{#unless nav-item--expanded}}
    hidden
  {{/unless}}>
  {{> @partial-block}}
</section>